1. What is the second law of thermodynamics?
2. What is isentropic flow and what are the two key assumptions required?
3. What is the speed of sound and what is its physical significance?
4. What is the Mach number?
5. What are the key differences between incompressible subsonic flow, compressible subsonic flow, transonic flow, and supersonic flow, and what are the approximate boundaries of these regimes?